EnvironmentBy

MUHAMMAD FAHAD ANSARI

12 IEEM 14

Why should we study Chemistry?Most of the World around us has a chemical basis.Consider many ways in which chemistry effects us.

Our body is a complex aggregate of chemical substances.

We depends on chemical processes for our life, because chemicals provide food, heat, light and the.

Other essentials such as cloths, building material, medicines, dyes, explosives are also made of chemicals.

3

Chemistry

4

What is Chemistry?

The science that deals with matter; its composition; its properties; the changes in composition that it will undergo; its relationship to energy; and the laws, principles, theories, and concepts that describe, interpret, and predict its behavior and basic nature.

6

Organic Chemistry is simply the chemistry of the compounds of the element carbon. In other words the properties of organic compounds are largely a result of the covalent bond.Except the carbon-containing compounds such as carbon dioxide, the carbonates, bicarbonates, and carbides.

Biochemistry: The chemistry that deals with the substances and reaction in living organisms.

7

Electrochemistry: the chemistry dealing with the effects of electricity on chemical reactions and the production of electricity through chemical processes.

Chemical reactions involve an electron exchange between the reactants. These reactions are called oxidation-reduction reactions or electrochemical reactions. There are two different classes of electrochemical reactions: those that produce electrical energy and those that are produced by electrical energy. 8

Analytical Chemistry: deals with the analysis of compounds and mixtures. Samples are separated into their component parts to determine what is present (qualitative) and how much (quantitative analysis).

Stoichiometry: refers to measurements and relationship involving substances and mixtures of chemical interest.

9

Nuclear Chemistry

The primary functions of atomic nuclei in the phenomena we have considered in establishing the masses of atoms and molecules and in furnishing a center of positive charge to keep electrons in position.

10

Periodic Table

11

Metals: They are good conductors of electricity; they contain only one or two weakly electrons in their outer energy levels.

Non-metals: They have relatively strong attraction for the electrons in their outer energy levels.

Metalloids: The elements whose properties are intermediate between those of the metallic and non-metallic elements.

12

Atomic Number: The number of protons in the nucleus of its atoms.

Atomic Mass: The sum of protons and neutrons in an atom.

Equivalent weight: The molecular weight of a substance divided by its combining capacity in the reaction.

Valence: The number of electrons an element gains, loses, or shares in forming a compound. 13

Electronegativity

14

15

16

17

18

Electro-negativity The bonds between two elements can be purely ionic, purely covalent, or anywhere in between depending on the elements involved.

The electro-negativity expresses the power of an atom in a molecule to attract shared electrons.

The electro-negativity values come from measurements of the strength of bonds between atoms and from measurements of the amount of electrical energy required to remove an electron from an atom of an element.

19

Fluorine (F) which has the strongest attraction for electrons of all the reactive elements is assigned an electro-negativity value of 4. All other elements are compared to fluorine.

According to Pauling (1901), if the difference between the electro-negativity values of the two elements is 2.0 or more, the bond is mainly ionic. If the electro-negativity difference is less than 2.0, the bond is mainly covalent.

20

Bonding between Elements

Ionic Bond: The electrostatic attraction that exists between positive ions formed when one atom loses electrons and negative ions formed by the atoms that gain the electrons.

Covalent Bond (Coordinate Covalent Bond): A bond between two atoms in which they are overlapping orbitals and sharing a pair of electrons, both of which originally belonged to only one of the atoms.

21

Ionic bond with: exchange of electrons to form stable octet; bond between a metal and nonmetal; example: NaCl, CaF2

Covalent bond with: sharing of electrons to form stable octet; bond between nonmetals; example: Cl2, N2

Polar covalent bond with: unequal sharing of electrons to form stable octet; example: H2O, NH3

Metallic bond with: sea of mobile electrons; bond between metals; example: Cu, Ag 22

Polar and Non-Polar Molecules Any diatomic molecule that has a non-polar

bond is non-polar. Example: All diatomic molecules: Cl2, N2, O2, etc… Otherwise, it will generally be polar.

Molecules that consist of 3 or more atoms are generally polar unless the following condition is met: If the central atom has no lone pairs and is surrounded by atoms of one element, then the molecule will be non-polar, for example, CO2.

23

Organic and Inorganic CompoundsThe distinction between the compounds found in the earth associated with rocks and soil and those associated with living organisms.

The two groups of compounds differ in their occurrence and in many of their properties.

The compounds associated with living organisms called organic compounds, and the earthy compounds are called inorganic compounds.

24

Table- Properties of Ionic and Covalent Compounds

Inorganic (Ionic) Compounds

Organic (Covalent) Compounds

1 Solids, often crystalline, relatively hard and brittle

May be solid, liquid, or gas, depending on the size of the molecules and the degree of intermolecular attraction (polarity and ability to form hydrogen bonds)

2 Relatively high melting and boiling points

Relatively low melting and boiling points, depending primarily on the size of the molecules and the amount of intermolecular attraction

3 Relatively soluble in water and insoluble in organic (non polar) liquids

Relatively insoluble in water and soluble in organic liquids; polarity and ability to form hydrogen bonds greatly increases water solubility

4 Electrolytes-solutions conduct electricity

Most are non electrolytes

5 Relatively stable to heat Relatively unstable to heat25